JPS6360247B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrodynamic bearing device in which a plurality of spiral grooves or the like are formed on a bearing sliding surface.

As a bearing device, a hydrodynamic groove bearing is known in which a plurality of spiral or herringbone grooves are formed on the sliding surface of the sliding bearing. Such a dynamic pressure groove bearing is a type of sliding bearing, and as it rotates, a working fluid such as oil is pushed into the bearing along a plurality of spiral grooves provided on the sliding surface, and high pressure is applied to the working fluid. The system generates fluid pressure and receives a load from this fluid pressure.

As the groove shape provided on the sliding surface, for example, a spirally curved groove with a substantially rectangular cross section and an angle between the longitudinal direction of the groove on the sliding surface and the rotating direction of the bearing is always constant. Grooves are generally provided on the sliding surface of either the rotating shaft or the bearing.

During operation of such a dynamic pressure group bearing, two opposing sliding surfaces are separated from each other by a fluid film, and both sliding surfaces rotate relative to each other in a non-contact state. For this reason,
Its features include almost no noise or vibration, and high dynamic rotation accuracy. In addition, since it has a structure in which grooves are provided on the sliding surface, it has the effect of providing better stability where the axial runout is small compared to a normal sliding bearing without grooves.

On the other hand, as such a hydrodynamic groove bearing,
Since the original dynamic pressure action does not occur during startup, the two sliding surfaces come into direct contact, and wear occurs due to the friction between the two sliding surfaces. Then, as the starting and stopping are repeated, the wear increases and the rotational accuracy is adversely affected. Therefore, as a countermeasure to this problem, the bearing material is selected to be a familiar material such as gunmetal, or a special lubricant is selected, but such measures do not require a special bearing material or lubricant. This may increase bearing costs.

In view of the above-mentioned points, an object of the present invention is to form a plurality of inclined grooves in the shaft hole of a bearing metal, to construct this bearing metal from a porous sintered alloy, and to form a porous portion of the sintered alloy. A special bearing material impregnated with oil and having grease of the same type and same kinematic viscosity as the oil interposed between the shaft inserted into the shaft hole and the shaft hole containing the groove. The object of the present invention is to provide a long-life, inexpensive hydrodynamic bearing device that does not require oil or lubricant.

The present invention will be explained below with reference to illustrated embodiments.

FIG. 1 shows a capstan motor for a deck, which is an application example of the hydrodynamic bearing device according to the embodiment of the present invention. The functions are described below.

In FIG. 1, a capstan shaft 11, which is the rotating shaft of the electric motor, is press-fitted into a rotor 12, which also serves as a flywheel, with the required inertia, and is fitted into a recess formed on the lower surface of the rotor 12. A multi-pole magnetized annular rotor magnet 13 is fixed thereto. The capstan shaft 11 is supported by a thrust receiver 15 fixed on the stator core 14, and has a base plate 17 fixed at a predetermined distance in parallel to the stator core 14 through support columns 16, 16. It is inserted into a bearing holder 19 which is fixed between a mechanical chassis 18 which is fixed in parallel above the base plate 17 at a predetermined distance.

Bearing metals 30, 30, which will be described later, are fitted into both ends of the bearing holder 19, and the capstan shaft 11 is rotatably supported by these bearing metals 30, 30. First stator core 1
4, a plurality of drive coils 20 are arranged concentrically with the capstan shaft 11 at a predetermined circumferential angle, and the upper surface of each coil 20 and the rotor magnet 1
3 and are opposed to each other with a predetermined gap between them.

Further, on the stator core 14, a position detection element (not shown) made of a Hall element or the like that detects the magnetic pole of the rotor magnet 13 is disposed at a position facing the rotor magnet 13, and based on this detection signal, a position detection element (not shown) is arranged. By controlling the energization to the drive coil 20, the rotor magnet 13 and rotor 12 are rotated as a known commutatorless motor, and the capstan shaft 11 is rotated together with the rotor 12. A concave portion 12a is also formed on the upper surface of the rotor 12, and internal teeth 22 are formed in the shape of an internal gear on the inner peripheral surface of this concave portion 12a.

Inside the recessed part 12a, there are upper and lower yokes 2 of a frequency generator fixed to the lower end of the bearing holder 19.
A ring-shaped excitation magnet 25 is disposed between the yokes 23 and 24 on the inner periphery thereof, and a generating coil 26 wound in a ring shape in the circumferential direction is further disposed outside the yokes 23 and 24. It is set up. Gear-shaped external teeth 23a are formed on the outer periphery of one yoke 23 of the frequency generator, and the internal teeth 22 and external teeth 23a face each other with an appropriate interval.

The power generating coil 26 detects magnetic changes between the internal teeth 22 and the external teeth 23a due to the rotation of the rotor 12, outputs a signal corresponding to the rotation speed of the rotor 12, and based on this detection signal, the driving coil 20 The rotor 12 is rotated at a constant rotation speed by controlling the energization to the rotor 12 .

A printed wiring board 27 is fixed to the lower surface of the stator core 14. The printed wiring board 27 includes a group of circuit elements (not shown) forming a drive control circuit for obtaining the output signal of the position detection element and the output signal of the frequency generator described above and controlling the energization of the drive coil 20. is installed. Note that the reference numeral 28 in the figure is a pinch roller that is pressed against the capstan shaft 11 and driven to rotate.
The rotation of the pinch roller 28 causes the tape or the like to run.

Now, to describe the hydrodynamic bearing device according to the embodiment of the present invention, in FIG. 1, the bearing metal indicated by the reference numeral 30 is the hydrodynamic groove bearing described at the beginning. The bearing metal 30 is formed into a sleeve shape, and a plurality of inclined herringbone-shaped grooves 30a are formed on the sliding surface around the shaft hole, as shown in FIG. Note that this groove may have a plurality of spiral shapes.

The bearing metal 30 is made of a porous sintered alloy, and the porous portions are impregnated with silicone oil having a kinematic viscosity of, for example, 1000 C/S. Note that this oil impregnation is carried out, for example, by a vacuum impregnation method under high temperature.

The capstan shaft 11 is fitted into the shaft hole of the bearing metal 30 configured in this way, and between the capstan shaft 11 and the sliding surface inside the shaft hole, there is a 1000C oil having the same kinematic viscosity as the oil described above. /S equivalent,
In addition, the same type of silicon-based grease 31 is interposed as shown in FIG. A large chamfered grease reservoir portion 30b is formed at one end of the shaft hole of the bearing metal 30, and a portion of the grease 31 is stored in this portion.

Note that the C/S mentioned above represents kinematic viscosity (centiStokes), and 1000 C/S is an example used in an experiment, and is not necessarily limited to this example. impregnating the bearing metal,
Oil equivalent to 1000C/S is made by adding additives such as oxidation and corrosion inhibitors to liquid base oil. Also, interposed between the shaft hole and the shaft,
Grease equivalent to 1000C/S is semi-solid by adding solid particle filler to base oil. In addition, as oil and grease,
Materials other than silicon may also be used. Note that the reference numeral 19a in FIG. 1 is an air vent, which is provided to make the air pressure inside the bearing holder 19 the same as the outside air pressure.

Here, when the motor shown in FIG. 1 is stopped, the capstan shaft 11 is also stopped, and in this state, a part of the outer circumference of the shaft 11 is on the sliding surface of the shaft hole of the bearing metal 30. are in contact.

From this stopped state, the motor starts and the shaft 11
At the initial stage when the bearing metal 30 starts to rotate, the oil impregnated in the bearing metal 30 achieves a lubricating function between the shaft 11 and the bearing metal 30.

On the other hand, after the motor starts and the shaft 11 starts rotating, the groove 30a of the bearing metal 30 (see Fig. 2)
Grease is pushed between the shaft 11 and the shaft hole of the bearing metal 30 along the axis, and due to a kind of pumping action, a fluid film 31 is formed between the two as shown in FIG.
a is formed, and due to the pressure of this fluid film, the shaft 11
is separated from the shaft hole, and the shaft 11 rotates without contacting the shaft hole. This kind of function is called dynamic pressure effect.

When the shaft 11 rotates without contacting the shaft hole, the porous portion of the bearing metal 30 made of sintered alloy is sufficiently impregnated with oil, and the grease 31 of the same kinematic viscosity is applied between the shaft and the shaft hole. Since the grease 31 is mixed with a filler, the filler does not enter the pores, and therefore the grease 31 is maintained as a fluid film 31a. .

Although the fluid film 31a moves with the rotation of the shaft 11, a grease reservoir 30b is provided, and the grease circulates between this portion and the shaft hole surface, so that the grease does not flow out. Prevented.

On the other hand, when the shaft 11 is in contact with the shaft hole surface of the bearing metal 30 when the motor is started, oil in the bearing metal flows toward the shaft 11 due to friction, and this oil causes a A lubrication function is achieved in between. Then, the oil flowing toward the shaft 11 advances to both ends of the bearing metal 30 and returns from both ends into the porous portion of the bearing metal, thereby performing a kind of pumping action.

In FIG. 1, when the pinch roller 28 presses the shaft 11, the shaft 11 tends to deflect due to this pressure, but due to the dynamic pressure action and the grease 3
Due to the pressure action of the fluid film 31a formed in 1,
The shaft 11 rotates while maintaining its central position.

In this way, the oil impregnated into the bearing metal made of porous sintered alloy and the grease interposed between it and the shaft to form a fluid film,
By having the same kinematic viscosity and using the same type of silicone, no dynamic pressure effect occurs.
When the shaft starts rotating, the oil in the bearing metal achieves a lubrication function, and after the shaft starts, a fluid film is formed by the grease, and this dynamic pressure action allows the shaft 11 to be supported in a non-contact state. Therefore, the shaft and bearing metal are less likely to wear out, and the life of the bearing device can be extended accordingly.

Further, since only general oil or grease is used, no special bearing material or lubricant is required, and the bearing device can be made inexpensive. Furthermore, for the supported axis,
Even if pressure is applied in a direction perpendicular to this axial direction, the amount of deviation of the shaft will be small due to the dynamic pressure effect that accompanies the formation of a fluid film by the grease. Even if direct contact occurs, the lubrication function is achieved by the oil impregnated within the bearing metal, so there is no risk of the shaft's rotation function being impaired, and it can also handle a wide range of load conditions. be able to.

As described above, according to the present invention, it is possible to provide a long-life, inexpensive hydrodynamic bearing device that does not require special bearing materials or lubricants, can maintain good rotational accuracy, and has a long life.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a capstan motor for a deck, with the main part taken in cross section, which is an example of application of the device according to the present invention, and Fig. 2 is a cross section of the bearing metal of the device according to the present invention. 3 are sectional views of the hydrodynamic bearing device of the same embodiment. 11... Axis, 30... Bearing memory, 30a...
Groove, 31... Grease, 31a... Fluid film.

Claims (1)

[Claims] 1. A hydrodynamic bearing in which a plurality of inclined grooves are formed in a shaft hole of a bearing metal into which a shaft is rotatably inserted, and lubricating oil is interposed between the shaft and the shaft hole including the grooves. The bearing metal is made of a porous sintered alloy, and the porous portions of the sintered alloy are impregnated with oil, and the same type of oil as the oil is provided between the shaft and the shaft hole as a lubricating oil. A dynamic pressure bearing device characterized in that a fluid film is formed by interposing grease of the same dynamic viscosity.